This invention relates to a control panel of an AC motor used in various fields, such as for driving the spindle or table of a machine tool.
An AC motor is controlled by an inverter. An inverter control circuit of this type is employed in an arrangement of the kind shown in FIG. 7. Specifically, the inverter control circuit includes an electromagnetic contactor 1, a reactor 2, a diode bridge 4 comprising diodes D1-D6, a smoothing capacitor 5, a discharge transistor 6 for regeneration, and a transistor inverter 7, these being connected to three-phase input terminals R, S, T of an AC motor. The AC motor (not shown) is connected to output terminals U, V, W of the inverter. In FIG. 7, numeral 3 denotes a control transformer, C1-C5 represent surge absorbing capacitors, and R1, R2 designate discharge resistors. Thus, a large number of electrical components are needed to control the AC motor by means of the inverter.
These electrical components are compactly arranged in a resin-molded housing 9 as shown, for example, in FIG. 8. Specifically, electrical components such as the electromagnetic contactor 1, reactor 2, control converter 3, diode bridge 4, smoothing capacitor 5, discharge transistor 6 for regeneration and transistor inverter 7 are arranged at predetermined positions inside the resin-molded housing 9. Each of these electrical components has connection terminals 14 led out onto its upper surface, each connection terminal being designed so as to be located on the same plane.
These electrical components ae interrelated and connected by short bars 15 fixedly secured to a short bar substrate 10 of the kind shown in FIG. 9. Specifically, the short bar substrate 10 having the short bars 15 affixed to its lower surface in correlation with the connection terminals 14 of the electrical components is placed on the electrical components, thereby connecting these electrical components in a predetermined relationship. Each short bar 15 is formed to include holes 16 at locations corresponding to the connection terminals 14 of the electrical components, each hole having a conductor fitted therein.
A printed circuit board (not shown) having electronic components mounted thereon is arranged on the short bar substrate 10 and these electronic components are connected to the electrical component assembly, thereby constructing the AC motor control panel.
Thus, the AC motor control panel comprises various electrical components, each of which is arranged in compact form. Accordingly, it is desired that the electrical connections be made automatically and reliably when each component is assembled. Further, when a control panel of this type fails as the result of a faulty electrical component or the like, it is desired that solely this portion of the control panel be capable of quick restoration.
An object of the present invention is to provide a control panel of the above type, in which the electrical components constituting the inverter control circuit of an AC motor can be electrically connected in reliable fashion at the time of assembly.